Conventionally, the RIE (Reactive Ion Etching), etching a surface of a wafer with ions, has been performed as a substrate processing that is performed on the wafer for a semiconductor device.
In the RIE processing, ions are generated by converting a processing gas that is introduced in a space facing the wafer into a plasma. The ions are accelerated by a self bias electric potential generated by applying RF power to a lower electrode, and the ions are collided with the surface of the wafer. Thus, the surface of the wafer is etched physically, thereby forming grooves (trenches) on the surface of the wafer. Since the accelerated ions proceed in a predetermined direction, the surface of the wafer is etched in the predetermined direction accordingly. Conventionally, in the RIE processing, trenches are formed vertical to the surface of the wafer.
Recently, miniaturization of integrated circuits formed by stacking semiconductor chips have been strongly demanded, and three-dimensional interconnections on the semiconductor chips have been strongly needed in order to increase stackability of the semiconductor chips. In other words, oblique etching (hereinafter, referred to as “angled etching”) with respect to the surface of the wafer has been strongly required on the wafers which constitute bases of the semiconductor chips.
In addition, an ion injection method has been known that injects ions from an inclined direction in an ion implant process, which injects ions into a bottom portion of the trench. However, since the advancing direction of the injected ions is inclined with respect to the depth direction of the trench in this method, the ions are injected to a sidewall of the trench and the sidewall is degraded. Thus, in order to prevent the ions from being injected to the side wall of the trench, it is required that the trench is formed obliquely with respect to the surface of the wafer by the angled etching.
In response to such needs, as a means for realizing the angled etching, a plasma etching apparatus has been recently developed that includes a support unit supporting the wafer obliquely with respect to the advancing direction of the ions to etch the surface of the silicon obliquely (for example, see Japanese Patent Laid-open Publication No. S57-164986). In addition, a plasma surface processing apparatus has been developed that includes a dipole ring magnet capable of being tilted to apply a tilted magnetic field thereto so that the ions are introduced obliquely to the surface of the wafer (for example, see Japanese Patent Publication NO. H7-94475).
However, the above-described plasma etching apparatus or plasma surface processing apparatus is problematic in that an inclined angle of the support unit or the dipole ring magnet needs to be changed when an etching angle in the angled etching is set to a desired value, which makes setting of a desired etching angle difficult. In addition, since the configuration of the above-described plasma etching apparatus or plasma surface processing apparatus is complicated, there is a problem that costs of the apparatuses are increased.